DESCRIPTION: The ability to recognize categorical relations is perhaps our most fundamental cognitive skill; categories summarize and organize our acquired knowledge, and allow us to extend our knowledge to new instances. The ability to categorize is particularly crucial in infancy, when much is to be learned about the world. Because of its importance, categorization, in infancy has been extensively studied over the past 20 years, focusing on whether infants attend to natural categories such as dogs, furniture, and trucks, and on how infants form categories of artificially constructed stimuli, such as geometric shapes, schematic animals, and line drawings of faces. The proposed research will further our understanding of the development of categorization skills in infancy by 1) demonstrating the relation between categorization in different procedures, and 2) assessing the roles of factors believed to contribute to the development of infants' use of their categorization skills. The present approach views categorization as a process that is more or less easily applied in different contexts. Thus, differences in categorization as a function of task (i.e., if infants respond to a particular category in some procedures but not others) are seen as task demands influencing how easily infants can use their categorization skills. This is not the same as a competence-performance distinction, in which tasks mask infants underlying competence and thus the demands of the tasks are seen as less important than that underlying competence. In the present perspective, task demands are an integral part of infants' forming categories. Thus, categorization skills are used in conjunction with other cognitive skills. Two sets of studies are proposed. First, infants' categorization in visual familiarization and object examining, two widely used assessments of categorization in infancy, will be compared. If a single process underlies categorization in different procedures, infants should form categories in the same way, and forming a category in one procedure should facilitate the formation of categories in subsequent procedures. This first set of studies will provide additional evidence that categorization in different procedures is a function of a single general process. The second set of studies will evaluate the factors that contribute to the development of infants use of those categorization skills. For example, procedures are assumed to require that infants use both their categorization and attentional skills. Thus, as infants develop they may be better able to simultaneously use both types of skills. This hypothesis will be tested by evaluating infants formation of categories in procedures that vary in the demands they place on infants attentional resources. In addition, increased knowledge about particular objects is assumed to contribute to why older infants more easily categorize items than do younger infants. Experiments will systematically assess the role of familiarity on infants' formation of categories.